Arc welding gun

ABSTRACT

A high current capacity arc welding gun for gas-shielded, continuous feed, consumable electrode arc welding processes. Features include: a unique handle cooled by convection air flow; an improved head assembly having a unique electrical insulating ion impervious shield for preventing destructive arcing to the gas nozzle, an improved shielding gas flow path through the head assembly which additionally cooperates with the ion impervious shield to prevent gas nozzle arcing, a unique current contact top which attaches to the head assembly by a novel curved wedge clamping concept and which is produced by an improved, versatile, and inexpensive method of manufacture that increases the copper density and refines the grain structure in the current contact tip for greater life; an improved gooseneck lining for longer life and reduced friction; a heat protected control switch assembly of rugged construction and unique trigger operation; and an improved welding cable connection assembly.

United States Patent 72] Inventors Arthur A. Bernard Beecher; Richard A.Bernard, Flossmoor, 111. [21] Appl. No. 840,582 [22] Filed June 5, 1969Division of Ser. No. 650,051, June 29, 1967, Pat. No. 3,469,070.

[45 Patented Apr. 27, 1971 73] Assignee Bernard Welding EquipmentCompany Beecher, Ill.

[54] ARC WELDING GUN 4 Claims, 17 Drawing Figs.

Primary Examiner-J. V. Truhe Assistant Examiner-George A. MontanyeAttorney-l-lume, Clement, Hume & Lee

ABSTRACT: A high current capacity arc welding gun for gasshielded,continuous feed, consumable electrode arc welding processes. Featuresinclude: a unique handle cooled by convection air flow; an improved headassembly having a unique electrical insulating ion impervious shield forpreventing destructive arcing to the gas nozzle, an improved shieldinggas flow path through the head assembly which additionally cooperateswith the ion impervious shield to prevent gas nozzle arcing, a uniquecurrent contact top which attaches to the head assembly by a novelcurved wedge clamping concept and which is produced by an improved,versatile, and inexpensive method of manufacture that increases thecopper density and refines the grain structure in the current contacttip for greater life; an improved gooseneck lining for longer life andreduced friction; a heat protected control switch assembly of ruggedconstruction and unique trigger operation; and an improved welding cableconnection assembly.

Patented April 27, 1971 mm mm 3 Sheets-Sheet. 1

. .Uwe. 9 he Bum TQE m Inventors Arthur, A. Bernard Richard A. Bernardfi Attorneys Pateiiiied A ril 27, 1971 3 Sheets-Sheet 8 Inventors ArthurA. Bernord Richard A. Bernard Attorneys Paiggnted April 27, 1971 3Sheets-Sheet 5 FIG.13

i T. r llllll i fi -mL r Inventors S y m m 0 m m rr Q ee A 8 A r r 0 hmg AR y B m ARC WELDING GUN This is a division of application Ser. No.650,051, filed June 29, 1967, now U.S.'Pat. No. 3,469,070.

This invention relates to arc welding guns used for applyinggas-shielded, continuous feed, consumable electrode arc weldingprocesses.

There has been a long standing need for an air-cooled arc welding gunwhich can handle a much higher range of welding current thanconventionally-designed air-cooled arc welding guns because theefficiency of all arc welding processes, measured by the rate at whichelectrode metal is melted and con verted into weld metal, is directlyrelated to the volume of welding current used to melt the electrode.Accordingly, it is a very important object of this invention to providean aircooled arc welding gun for gas-shielded, continuous feed,consumable electrode arc welding processes which is capable of handlinga range of welding current up to 800 plus amperes at a 60 percent dutycycle as compared to the top range of about 500 amperes at a 60 percentduty cycle to which present conventional air-cooled arc welding guns aregenerally limited.

The problems which must be solved in developing an aircooled gun whichhas a capacity for handling an additional 300 amperes of welding currentcannot be solved simply by increasing the size or electricalconductivity of those parts of conventional arc welding guns whichconduct the welding current or by increasing the size of the weldingcurrent cable connected thereto. Since an understanding of the problemsinvolved will aid in understanding the present invention, it will behelpful to discuss some of these problems at this point.

Increasing the size of the arc welding gun to increase its weldingcurrent capacity increases the effort that is required for manipulatingthe gun along the course of welding when the seams to be welded arelocated in confined and cramped areas. Accordingly, it is another objectof the present invention to provide an ultrahigh current capacityair-cooled arc welding gun which is not larger in overall size thanconventional arc welding guns which are limited to a much lower range ofwelding current.

Adding weight to an arc welding gun to increase its current conductingcapacity increases operator fatigue, and, hence, welding operatorseither resent or refuse to use guns which weigh more than conventional.Consequently, another object of this invention is to provide an arcwelding gun which weighs no more than conventional arc welding guns witha much slower welding current capacity. This low weight feature was madepossible primarily by reducing the number of parts comprising the arcwelding gun. For example, that portion of conventional arc welding gunscommonly called the body portion has been completely eliminated.

One principal factor which determines the current handling capacities ofan arc welding gun is the maximum permissible temperature of the handleof the gun. The limiting temperature of the handle of an arc welding gunis 140 F. If the handle exceeds 140 F., even by 1 or 2, it may blisterthe operators hand. Therefore, in the arc welding gun of the presentinvention, the handle does not exceed 140 F. even though this gunoperates at a much higher range of welding current than conventionalair-cooled arc welding guns. This achievement was attained byrecognizing and accepting the fact that it is not resistance heatingwithin the arc welding gun that is the principal cause of the hightemperatures encountered in arc welding guns but rather the radiatedheat of the arc itself which is picked up by the current contact tip andhead member and conducted back through the welding gun into the weldingcurrent cable where it is dissipated by radiation. Thus, increasing theelectrical conductivity of the current conducting parts of the arcwelding gun will not effectively reduce the temperature to which the gunis heated during prolonged periods of welding. Nor has circulating wateror other coolant through the current conducting members of the gun, asin conventional water-cooled guns, made it possible to maintain thehandle sufficiently cool to operate at the high current range now madepossible with-the present invention. The higher the welding current tothe arc, the higher is the heat conducted back through the gun into thewelding current cable, and'even in water-cooled guns this high heat flowthrough the handle cannot be prevented by the conventional circulationof coolant through the current conducting members of the gun. In fact,one of the primary objects of the present invention is not only toeliminate the original investment cost of such liquid cooling apparatusand the cost of maintaining such apparatus but additionally to providean air-cooled gun capable of handling at least 200 amperes more weldingcurrent than is handled by conventional water-cooled guns. In thepresent invention, the high heat flow through the gun to the weldingcurrent cable is accepted, but the handle of the gun is not highlyheated. Specifically, it is a very important object of the presentinvention to efficiently insulate the handle of the arc welding gun fromthe highly heated current conducting parts contained therein byproviding a tubular handle which is open at both ends and telescopedover the metal parts which conduct heat through the handle from the arczone and back into the welding cable and which is mounted so as to spacethe interior surface of the handle from the exterior surfaces of theseheat conducting metal parts, thereby forming effectively a ventilatingduct between these surfaces which extends the total length of the handleand is open at both ends. As will be more fully described further on,the heated metal parts extending through the handle opening cause airconvection in and through the handle opening, cooling the exteriorsurfaces of these metal parts and the interior surfaces of the handle.This structure is clearly distinct from the design of conventionalair-cooled arc welding guns in which the so-called body portion withinthe interior of the handle completely fills or blocks the interior ofthe handle, thus totally preventing any cooling circulation of airthrough the handle as occurs in the present invention.

Another very difficult problem which had to be solved to provide thehigh current capacity arc welding gun of the present invention was theproblem of electrically insulating the gas nozzle from the weldingcurrent circuit plus shielding the gas nozzle from the high density ofions which is developed around the welding current circuit memberswithin the gas nozzle when these contained circuit members are chargedwith the new high range of welding current and highly heated byradiation from the are because this high density of ions is capable ofproviding a conductive path for the welding current from the containedcircuit members when the dimension between the gas nozzle and theworkpiece is equal to or less than the dimension of the welding arc. Itwas established during extensive development in creating this inventionthat this coronalike condition which surrounds the head member of thegun, the current contact tip, and that portion of the electrode whichextends from the current contact tip to the welding arc is capable ofinitiating a destructive arc to the gas nozzle. Accordingly, the gasnozzle must not only be electrically insulated from the welding currentcircuit, but must also be shielded from the high density of ionssurrounding these three parts of the welding current circuit. Inaccordance with the present invention, therefore, an ion impervioustubular shield is interposed between the gas nozzle and the head memberin the arc welding gun. This ion impervious shield is a unitary membersince if it were of two or more pieces, the small seam or separationbetween the pieces even of a few thousandths of an inch would permit aseepage of ions through the seam or separation to kindle an are betweenthe head member and the gas nozzle and then from the gas nozzle to theworkpiece. Moreover, neither the gas nozzle nor its attaching means canextend rearwardly of this tubular ion impervious shield, or arc ing withthe terminus of the gas nozzle attaching means will result.

The gas nozzle itself is formed from a short length of copper or brassthin-wall tube in a punch press operation. Accordingly, it is easily andinexpensively formed. Moreover, since the wall of the nozzle ispurposely thin, spatter which accumulates on the nozzle can be removedquickly and simply by tapping or rapping the side of the nozzle againstthe weldi ment or other surface. This cracks-the ring .of brittlespatter into small pieces which fall from the nozzle.

As will be seen from the detailed description, the head member of thearc welding gun of the present invention is provided with an annulararrangement of shielding gas outlet ports, which ports are inclinedforwardly with respect to the axis of the head member so that the gasflow impinges tangentially against the interior surface of theinsulating member and flows along the interior surface of the insulatingmember and the gas nozzle in an annular configuration which serves topurge the space adjacent the interior surface of the gas nozzle at itsforwardmost end which is not protected by the tubular shield in order toprevent high ion density in this region. in short, the tubular ionimpervious shield coacts with the particular form of gas flow inpreventing arc initiating conditions adjacent the surfaces of the gasnozzle. Moreover, the particular arrangement of angularly oriented gasports have their exit orifices or openings in a cylindrical outersurface of the head member, thereby reducing the possibility of pluggingthe gas ports with weld spatter.

The control switch assembly on the present arc welding gun is mounted onthe exterior surface of the handle to isolate the switch assembly fromthe high volume of heat radiating from the suspended main trunk whichextends through the handle. Only two small openings through the handleare necessary for passage of two control wires through the handle forattachment to the terminals of the switch. Moreover, since the switchassembly is mounted on the outside of the handle, it must be of a shapeand construction to withstand rough usage. Accordingly, it is animportant object of the present invention to provide a control switchassembly meeting these requirements. As will be seen from the detaileddescription further on, the control switch assembly of the presentinvention meets these requirements with a construction which is uniqueboth in structure and operation.

Another important aspect of the present invention is the welding currentcontact tip which is characterized by a number of markedly advantageousfeatures. As is well known,

the life of a current contact tip under certain conditions is limitedand may be measured in terms of hours. For example, when the electrodebeing deposited is 3/32-inch diameter or larger, and when knurled feedrollers are used in the electrode feeding machine, the knurled feedrollers roughen the surface of the electrode causing actual rasping outof the bore of the current contact tip as the electrode is fedtherethrough. Therefore, it is another very important object of thepresent invention to provide a current contact tip which, because of itsstructure and its method of manufacture, is less expensive thanconventional current contact tips, yet has a greater useful life thanconventional current contact tips. Conventional current contact tips arenormally threaded for threaded engagement in the bore of the headmember. However, threading the current contact tip not only increasesits cost but also provides a form of connection to the head member whichis attended by several problems as will be described further on. Theconventional threaded current contact tip costs the user about $2.00apiece on the market, whereas the current contact tip of the presentinvention costs the user approximately one-fourth of that amount.Moreover, the useful life of the current contact tip of the presentinvention under the abrasive action of the roughened surface electrodeis about twice that of a conventional threaded current contact tip.Accordingly, for large fabricators, who deposit many tons of electrodemonthly, and thus use thousands of current contact tips monthly, thesavings may amount to many thousands of dollars monthly. This inventionmakes possible such cost saving for two principal reasons: (1) thedesign or structure of the current contact tip was developed to be verysimple and to provide low cost manufacture, and (2) a greater life forthe current contacttip of this invention is provided by purposelyaltering and refining the arrangement of grain formation of the copperand increasing the hardness of the copper by the unique method ofmanufacture described herein. For example, the Rockwell C hardness ofthe commercial copper tubing from which the current contact tip of thisinvention is manufactured averages 8 to 12, and this hardness isincreased by the method of manufacture of the present invention to anaverage of 30 to 40, an increase of over 300 percent. As will be seenfrom the ensuing detailed description, the current contact tips of thepresent invention are made from commercial size copper tubing. Thecopper is actually compressed into a state of greater density as thecommercial copper tube is converted to the dimensions required toproduce the current contact tip of the present invention. In thisregard, it is important that the method of manufacture of the presentinvention not be likened to a conventional swedging operation in whichthe size of the bore of a copper tube is not reduced by a thickening ofthe wall, but rather by reducing the outside diameter of the tube andretaining the wall thickness with a corresponding reduction in thediameter of the bore. in the method of the present invention, the wallthickness itself is altered.

As previously noted, the threaded connection generally used onconventional current contact tips is attended by serious problems.During the life of-a contact tip, the tip is heated many, many times toan extremely high temperature during welding and then permitted to coolwhen welding stops. This repeated heating and cooling results in aslight loosening of the threaded connection with each cycle of heatingand cooling which necessitates frequent retightening and if thetightness is not maintained, an arcing develops between the two threadedsurfaces which destroys the threads and this, in turn, necessitatesrethreading or discarding both of these parts. Also, being made of softcopper, the threads are easily and frequently damaged in handling. Thecurrent contact tip of the present invention is held within the bore ofthe head member by a binding force developed by a unique cam actionsurface as will be completely described in the ensuing detaileddescription. As will be seen, the unique cam action attachment isarranged to accommodate slight flexure of the current contact tip toeliminate loosening due to thermal expansion and contraction.

The electrical connection necessary between the current contact tip andthe electrode itself is obtained in the present invention by impartingto the continuous electrode, just before it reaches the current contacttip, a curved configuration so that the curved electrode produces itsown spring force for making efficient electrical contact as thecurvature of the electrode is straightened out in passing through thestraight bore of the current contact tip. Accordingly, it is anotherimportant object of the present invention to provide an improved curvedgooseneck portion of the gun within which electrode is curved to insureefficient welding current contact with the electrode within the currentcontact tip. More specifically, it is an object of the present inventionto reduce the amount of friction along the inner surface of thegooseneck portion and the surface of the electrode as the electrode isfed therethrough in order to reduce the force required to push theelectrode through this portion of the arc welding gun. In addition, itis an object of the present invention to increase the life of thegooseneck portion of the arc welding gun. In conventional practice, toprovide for efficient conduction of welding current through thegooseneck portion of the welding gun, the gooseneck portion isfabricated of copper in the form of a tube or pipe. The copper tube orpipe may or may not be lined with a common steel or stainless steeltube. Being harder than copper, such conventional steel liner tubes doincrease the life of this portion of the gun and, to a minor extent,reduce the magnitude of force required to push the electrode throughthis portion of the arc welding gun. ln accordance with the presentinvention, however, the gooseneck portion of the gun is improved bylining the gooseneck with a series of short length bushings made ofextremely hard alloyed steel or tungsten carbide. By increasing thehardness of the surface over which the soft steel electrode is slid, thefriction is reduced proportionately. Therefore, the amount of forcerequired to push the electrode through'hardened steel or tungsten steelCarbide bushings is reduced to a minimum, as is the rate of wear.

- It is stillanother object of the'present invention to provide animproved system for connecting the rearward terminus of the arc weldinggun to the flexible conduit through which the electrode is fed to thegun. The conventional flexible conduit consists of a helical spring wireformed as a tube. In accordance with the present invention, the maintrunk of the arc welding gun at its rearward portion is provided with athreaded bore having the same pitch as the helical pitch of the springwire forming the flexible conduit. -The flexible conduit is thenconnected to the arc welding gun by threading it into this bore.

As will be apparent to those skilled in the art, many of the uniquestructural features of the subject arc welding gun which cooperate tomake'possible its ultrahigh welding current capacity may also beemployed to great advantage in arc welding guns operating atconventional current levels, in arc welding guns for submerged arc andself-shielded arc welding processes, and in other applications.

These and other features and objects of the present invention will bebetter understood by reference to the following detailed description andthe accompanying drawings.

IN THE DRAWINGS FIG. 1 is a side view of the arc welding gun for thepresent invention partially in cross section and partially in elevation.

FIG. 2 is an enlarged cross-sectional view taken at 2-2 of FIG. 1.

FIG. 3 is an enlarged cross-sectional view taken at 3-3 of FIG. 1.

FIG. 4 is an enlarged cross-sectional view of the head portion of thearc welding gun.

. FIG. 5 is a cross-sectional view taken at 5-5 of FIG. 4. FIG. 6 is across-sectional view taken at the same location as FIG. 5 but showinganother form of the present invention.

FIG. 7 is a cross-sectional view also taken at the same location as FIG.5 but showing still another form of the present invention.

FIG. 8 is an enlarged top view in elevation of the control switchassembly of the present invention mounted on the handle of the arcwelding gun and shown in released position.

FIG. 9 is an enlarged side view of the control switch assembly mountedon the handle of the arc welding gun and shown partially in elevationand partially in cross section and in locked position.

FIG. 10 is another enlarged view of the control switch assembly shownpartially in cross section and partially in elevation and in depressedposition.

FIG. 11 is an enlarged view of the trigger member utilized in thecontrol switch assembly.

FIG. 12 is an enlarged view in elevation of the current contact tip ofthe present invention.

FIG. 13 is an enlarged side view partially in elevation and partially incross section of a short section of copper tube cut from a random lengthof commercial size seamless copper tube from which the current contacttip of the present invention is formed.

FIG. 14 is an enlarged side view partially in cross section andpartially in elevation illustrating the product of one step in themethod of manufacture of the current contact tip in accordance with thepresent invention.

FIG. 15 is an enlarged side view partially in elevation and partially incross section illustrating the product of another step in the method ofmanufacture of the current contact tip in accordance with the presentinvention.

FIG. 16 shows the operation of a punch press die according to thepresent invention by which the length of copper tube section shown inFIG. 13 is shortened to increase the thickness of the copper in order toproduce the element shown in FIG. 14.

with the method of the present invention to extrude the diameter of thetube section shown in FIG. 14 to reduce both the inside diameter and theoutside diameter in order to produce the element shown in FIG. 15.

Referring now to FIG. 1, it is seen that the arc welding gun comprisesbroadly a main trunk 21 on which is mounted a welding cable connectorassembly 23, a handle 22, and a head assembly 24. The handle 22, inturn, carries a control switch assembly 25. The main trunk 21 is theprincipal structural support element of the subject arc welding gun andthe means by which the consumable electrode 28, the shielding gas, andthe welding current are conducted to the head assembly 24 of the gunwhere these materials are combined to produce the particular type of arcwelding process. Accordingly, it is believed that the most logicalformat for presenting the detailed description of the subject arcwelding gun'is to describe first the main trunk 21 and then the variousother structures of the arc welding gun in the order they are carried onthe main trunk 21 proceeding from the rearward end to the forward endthereof. The reader, however, is requested to bear in mind that thestructures are not necessarily being presented in their order ofimportance.

THE MAIN TRUNK Themain trunk 21 comprises basically a rigid thick-walledcopper pipe 35., For the straight portion of its length through thehandle 22, the copper pipe 35 is preferably provided with a steel linertube 36. Fromthe forward end of the handle 22, the copper pipe 35 iscurved'as a gooseneck for the twofold purpose of (l) facilitating themanual deposition of weld metal and (2) forming the electrode 28 into acurve just prior to its passage through the current contact tip 37 sothat the curved electrode provides its own spring force for makingefficient electrical contact with the current contact tip 37 as itpasses through the straight bore 38 (FIG. 2) of the current contact tip.The radius and angular extent of the gooseneck curve are preferablyrelated to the size of electrode the gun is intended to handle to insureproper electrical contact as the electrode passes through the currentcontact tip bore 38. For example, for .an arc welding gun intended tohandle 3/32-inch to s-inch diameter electrode, the gooseneck portion ofthe pipe 35 is preferably curved through an arc of approximately 30 at aradius of approximately 4 inches. It is a unique feature of the presentarc welding gun that the gooseneck portion of the copper pipe 35 islined with a series of hardened steel or tungsten carbide straight-borebushings 39 serially disposed in end-to-end relationship as shown inFIGS. 1 and 4 and locked in position by the additional hardened steel ortungsten carbide bushing 41 which abuts the peened-over lip 42 at theextreme forward end of the copper pipe 35 (FIG. 4). The extremely hardbushings 39 serve to prolong the life of the gooseneck portion of thecopper pipe 35 and reduce the push force required to feed the electrodethrough the gun. Depending upon the radius of the gooseneck section ofthe copper pipe 35, the length of the individual bushings 39 should notexceed a factor of six times the bore of the bushings. To preventkinking of the electrode, the bore of the bushings 39 should not exceedtwice the diameter of the smallest diameter electrode to be handled, yetat least 9 percent larger than the largest diameter electrode to behandled. By way of example, the individual length of the bushings 39 mayvary between $6 and inch The exterior surface of the gooseneck portionof the copper pipe 35 is covered with a tubular jacket 43 of electricalinsulating material such as braided or laminated glass fiber orneoprene.

The bore 44 of the main trunk 21 conducts both the electrode 28 and theshielding gas to the head assembly 24 of the gun. To introduce theshielding gas into the bore 44, a copper tube 45 is provided whichextends through the wall of the copper pipe 35 and the liner 36 tocommunicate with the interior bore 44 of the main trunk. Connection withthe shielding gas source (not shown) is obtained by telescoping the gashose 46 over the rearward end of the tube 45' -As previously noted, themain trunk 21 also serves to coni duct the welding current to the headassembly 24 of the weld- THE CABLE CONNECTOR ASSEMBLY It is conventionalpractice in continuous feed, consumable electrode welding operations tofeed the electrode to the welding gun through a flexible conduit whichalso forms the core of the welding cable. An electrode feeding apparatusis conventionally employed to push the electrode through this flexibleconduit to the welding gun. In FIGS. 1 and 2, the welding cable isidentified by reference numeral 26, and the flexible conduit isidentified by reference numeral 27. As shown, the flexible conduit 27comprises a rather heavy gauge spring wire helically formed as a tube.To prevent kinking of the electrode, the inside diameter of the conduit27 should not exceed twice the diameter of the smallest diameterelectrode 28 to be fed through the conduit 27. However, the insidediameter should be at least 9 percent larger than the largest diameterof the electrode 28 to be fed through the conduit 27. For example, a0.160 inch inside diameter conduit is suitable for three thirty-secondsinch, seven sixty-fourths inch, and iii-inch diameter electrodes. Toprovide proper stiffness and sufficient flexibility, the conduit 27 forthese three sizes of electrode should be made from spring wire of about0.084-inch gauge. As best shown in FIG. 2, the welding current cable 26overall consists of several conductor cable elements 29 which arehelically wrapped about flexible conduit 27 and a jacket 31 composed ofrubber or neoprene material for electrically insulating the conductingcable elements 29. The connector assembly 23 provides a uniquearrangement for connecting the welding cable 26 and its internalflexible conduit 27 to the arc welding gun. The connector assembly 23comprises a cylindrical member 32 which is tightly threaded by taperedthreads onto copper pipe 35 to form the rearward end of the main trunk21. The member 32 is uniquely provided with an axial bore 33, therearward portion of which is enlarged and provided with threads of thesame pitch as the pitch of the helical turns of spring wire forming theflexible conduit 27. Thus, the flexible conduit 27 is easily and quicklyattached to the member 32 simply by threading its end into the bore 33wherein it is held very securely. The several conducting elements 29 ofthe welding cable 26 are bound to the outer surface of the member 32with a tightly wrapped length of wire 34 and then soldered to the member32 to provide an efficient electrical connection. This means ofconnecting the welding cable 29 to the member 32 prevents anypossibility of the flexible conduit from turning and becomingdisconnected from the member 32.

THE AIR FLOW HANDLE As previously noted, the principal cause of hot gun"condipending on the duty cycle time. Yet the outer surface of the handle22 must not exceed 140 F. The air flow handle 22 construction of thepresent invention makes it possible to maintain the handle surfacesufficiently low in temperature despite such ultrahigh current weldingconditions.

The handle 22 is a self-supporting tubular member having a longitudinalbore 47 of circular cross-sectional configuration which is open at bothends and which is telescoped over the rearward portion of the main trunk21. It is preferably fabricated of vulcanized paper base fiber althoughother electrically insulating and low heat conductivity materials may befound useful. Referring to FIGS. 1 and 3, it is seen that the handle 22is carried and spaced from the highly heated copper pipe 35 by two pairsof projections 48. Each pair of projections 48 is preferably formed of asection of brass tube 49 which is silver soldered or otherwise securelyfastened in a transverse recess in the periphery of the copper pipe 35as shown in FIG. 3. Inserted within the bore of each of the brass tubes49 is a heat resistant bushing 51 of resin bonded asbestos fiber orother suitable heat insulating and electrical insulating material. Thehandle 22 is mounted on the projections 48 by self-threading screws 52which are each passed through the handle and threaded into one of thebushings 51. The screws are thereby insulated from both the heat andelectricity of the main trunk copper pipe 35.

The open bore 47 of the handle effectively forms a columnar ventilatingduct enabling convection flow and circulation of cooling air along theexterior surfaces of the main trunk 21 and the interior surfaces of thehandle 22. It is this unique structure which maintains the handle 22sufficiently cool despite ultrahigh current operation of the gun. Thebore 47 preferably has a diameter which is at least 1% times larger thanthe outside diameter of the main trunk 21 to promote flow or circulationof a sufficient quantity of ambient air for cooling.

THE CONTROL SWITCH ASSEMBLY As previously noted, the control switchassembly 25 is mounted on the exterior surface of the air-cooled handle22. In this way, the control switch assembly 25 is isolated andprotected from the high volume of heat radiated by the main trunk 21.However, since the control switch assembly is mounted on the outside ofthe handle, it must be of a structure to withstand rough usage, yetoperate reliably.

The structure of the control switch assembly 25 is shown in FIGS. 1, 2,8, 9, and 10. As seen, the control switch assembly 25 is provided with ahousing 53 which is open at its rearward end to accommodate movement ofthe trigger member 54. The housing 53 is secured to the handle 22 by apair of selflocking screws 55 which are passed through housing sideflanges 56 and threaded into nuts 57 which are in the form of hollowtubes riveted to the handle 22. The flanges 56 are shaped to conform tothe tubular shape of the handle 22 to promote stable mounting of thecontrol switch assembly 25. To provide ruggedness, the switch housing 53is preferably of one-piece construction, deep drawn and formed to theshape shown from l6-gauge steel. Although shown mounted on the top ofthe handle 22, the control switch assembly 25 may conveniently bemounted on either the top or the bottom of the handle as a matter ofchoice.

tions is the heat radiated from the welding arc itself to the currentcontact tip and the head member of the gun and conducted back throughthe arc welding gun by the welding current conducting elements of thearc welding gun, through the handle of the gun and into the weldingcurrent cable, establishing a thermal gradient along the length of thewelding current cable. Obviously, the higher the welding currentconducted to the arc, the higher is the heat conducted back to thehandle of the gun into the welding current cable. For example,

in the present air-cooled arc.welding gun when operating at 800 ampereswith a 35-volt arc, the main trunk copper pipe 35 can become heated to atemperature upward to 400 F. de-

A conventional norrnally-open, snap-action electrical switch 58 isprotected by a band 59 of fibrous material and securely mounted to theswitch housing 53 by a pair of mounting pins 61 passed through thehousing 53, the fibrous band 59, and mounting bores which extend throughthe switch 58. The pins 61 are the spring-loaded type for retention andfor easy and quick removal of the switch 58', should this becomenecessary.

The switch housing 53 is provided with an interior trigger guide surface62 which may be concave for streamlining as shown or flat. The actuatorbutton 63 of the switch 58 is biased outwardly toward the trigger guidesurface 62. A forward portion of the elongate trigger member 54 isinterposed between the trigger guide surface 62 and the actuator button63. The trigger member 54 is curved compatibly with the trigger guidesurface 62 and is provided with a manually manipulative configuration 64at its rearward exposed end. At its forward end, the trigger member 54is provided with an elongate aperture 65 best shown in FIG. 11. A leafspring 66 is interposed between the trigger member 54 and the actuatorbutton 63. A bushing 67 is riveted at one end to the portion of theswitch housing 53 which forms the forward end portion of the triggerguide surface 62. As best shown in FIG. 9, the free end of the bushing67 extends through the elongate opening 65 at the forward end of thetrigger member 54. A screw 68 passed through the forward end portion ofthe leaf spring 66 and threaded into the bushing 67 attaches the forwardend of the leaf spring to the free end of the bushing 67. The bushing 67thus serves as a rigid base from which the leaf spring 66 iscantilevered rearwardly. The length of the shank 69 of the bushing 67 isapproximately 30 percent greater than the thickness of the triggermember to permit up and down movement of the forward end of triggermember 54 on the bushing 67, and the length of the elongate opening 65in the trigger member is approximately V4 inch greater than the outsidediameter of the bushing shank 69 to permit forward and rearward or inand out motion of the trigger member 54.

To understand the action of the control switch assembly 25,

'it should be noted that the leaf spring 66 has a step 71 approximatelymidway in its cantilevered length so that the rearward portion 70 of theleaf spring adjacent the actuator button 63 is stepped toward but is notin contact with'the actuator button when the switch is in the OFFposition. When the trigger member 54 is in its rearwardmost position,the forward apex of the step 71 of the leaf spring 66 bears against theunderside of the trigger member 54, holding the trigger member tightlyagainst the trigger guide surface 62 and providing the bias forcerequired for returning the trigger to the up OFF position from thedepressed ON position. The rearward portion 70 of the leaf springperforms as a resilient finger for actuating the switch button 63 whenthe trigger member 54 is depressed. Thus, for short periods of welding,the trigger member 54 in its rearwardmost position is simply depressedby thumb or finger pressure against the portion 64 which causes thetrigger member 54 to pivot downwardly about its forward end to ONposition causing the stepped portion 70 of the leaf spring 66 to depressthe actuator element 63 to close the switch 58. Upon release of downwardpressure on the trigger member 54, the trigger member 54 is returned tothe OFF position by the leaf spring 66, opening the switch 58.

To enable the trigger member 54 to be locked in ON position, a raisedsemispherical projection is provided onthe underside of the triggermember 54. The projection 72 registers with the stepped portion of theleaf spring 66 when the trigger member 54 is in its rearwardmostposition, as illustrated in FIG. I. To lock the trigger member 54 in ONposition, the trigger member is not pressed downwardly as describedabove for short period welding but rather is pushed forwardly intoabutment with the forward wall of the housing 53, thereby causing theprojection 72 on the trigger member to slide up and over the step 71 inthe leaf spring 66, causing the stepped portion of the leaf spring 66 todepress the actuator element 63 as illustrated in FIG. 9. The triggermember is securely held in this locked position by the force of the leafspring 66.

A salient safety feature is provided by the provision of an inwardprojection 78 at the rearward end of one of the sidewalls of the switchhousing 53. The projection 78 registers with a cutout 79 appropriatelylocated in the adjacent side of the trigger member 54 so that theprojection 78 does not interfere with the normal up-and-down pivotalaction of the trigger member 54 in its rearward unlocked position.However, as seen in FIG. 10, the projection 78 lies within the cutout 79when the trigger member is in depressed position thereby preventing thetrigger member from being moved forwardly to Incl! nnsitinn whiledenressed. Thus. the potentially dangerous situation of the weldingoperator unknowingly locking the gun in ON condition is averted. Theupward step 71 of the leaf spring also serves to impede any possibilityof inadvertently moving the trigger member 54 to lock position while itis depressed for short time welding. Another correlative safety featureis also provided by the projection 78. As seen in FIG. 9, when thetrigger member 54 is in forward locked position, the downwardly-inclinedrearward end of the arcuate portion of the trigger member 54 is disposedabove the projection 78. Thus, downward pressure on the manipulatingportion 64 of the trigger member causes the trigger to moye rearwardlyout of lock position. Hence, the trigger member 54 is readily unlockedby downward and/or rearward force.

The pair of wires 81 and 82 (FIGS. 1 and 2) connecting the snap actionswitch 58 to a control relay (not shown) or otherwise connecting theswitch 58 for ON/OFF welding current and electrode feed control arepassed through two small openings 83 and 84 (FIG. 1) through the handle22. Thus, it

can be appreciated that the present invention provides a control switchassembly which is rugged, well protected from the high heat condition ofthe main trunk 21, and characterized by advantageous operating action.

THE HEAD ASSEMBLY Moving on now to consideration of the head assembly 24of the arc welding gun best shown in FIG. 4, it is seen that thisassembly comprises basically the head member 86, the current contact tip37, the tubular shield 89, and the gas nozzle 91. The cylindrical headmember 86 is fabricated of brass or other rugged,electrically-conductive metal and is provided with a central axial bore87, the rearward portion of which is provided with a tapered thread fortight electrically-conductive threaded connection onto the forward endof the copper pipe 35. The rearward portion of the copper currentcontact tip 37 is telescoped within the forward portion of the bore 87.As previously noted, the electrode 28, having been previously curved inpassing through the gooseneck portion of the main trunk 21, provides itsown spring force for efficient electrical contact with the currentcontact tip 37 as it passes through the straight bore 38 of the currentcontact tip. The unique structure of the current contact tip 37 and itsunique threadless connection to the head member are important featuresof the present invention which will be described in detail further on.

The metal gas nozzle 91 is telescoped over the tubular insulator and ionshield 89 which, in turn, is telescoped over the head member 86. Thetubular shield 89 and the gas nozzle 91 are securely clamped in place byan annular, adjustable clamp 97.

It is important to understand the nature and purpose of the tubularshield 89. As previously noted, it has been found that in very highcurrent welding operation, a high density ion field or coronalikecondition is developed around the head member 86, the current contacttip 37, and the portion of the electrode 28 projecting forwardly fromthe current contact tip. It has been further found that because of thishigh density ion field, merely spacing the gas nozzle 91 from thesecurrent conducting members with electrical insulating material does notsuffice to prevent arcs from developing between the gas nozzle and theworkpiece. These unwanted arcs quickly work severe dissipation damage tothe gas nozzle and current conducting members affected. In the presentinvention, the tubular shield 89 both electrically insulates the gasnozzle 91 from direct contact with the current conducting members of thegun and shields the gas nozzle and its attaching means from the highdensity ion field to prevent arcing to the gas nozzle. The tubularshield is of seamless, one-piece construction and is formed of hightemperature accommodating material which is both electrically-insulatingand ion impervious. For example, the tubular shield may be formed oflaminated glass cloth in which the layers of glass cloth are bondedtogether with a silicone resin, N.E.M.A. grade G7. A wall thickness ofone-sixteenth inch for the tubular shield 89 has been found practicalwith this material. Another material which may be used in braidedasbestos filled with silicone resin. The tubular shield 89 extends froma point of abutment against an annular shoulder 92 at the rearwardterminus of the head member 86 to a point forwardly of the forward endof the head member 86. A centrally recessed washer 93 of electricalinsulating material is provided to cover the annular shoulder 92 inorder to e|ectrically insulate this portion of the head member 86.

The gas nozzle 91 is of thin wall brass construction. It is preferablyprovided with longitudinal slots at its rearward end so as to beradially contractable as described in Bernard et al. U.S. Pat. No.3,283,121. Toward its forward end, the nozzle 91 is brought to a smallerinternal diameter by an annular step 94. The gas nozzle is dimensionedsuch that, when it is telescoped onto the tubular shield 89, the forwardend of the tubular shield 89 abuts against the step 94, and the rearwardend of the gas nozzle 91 does not reach to the rearward end of thetubular shield 89. Thus, the rearward end of the tubular shield 89purposefully extends slightly beyond the end of the gas nozzle 91,preferably at least M; inch beyond the end of the gas nozzle. Thisextension of the tubular shield 89 beyond the end of the gas nozzle isimportant. It provides a separation dimension between the rearward endof the gas nozzle 91 and the ion density around the head member 86 atthe end of the tubular shield 89. If this separation were not provided,the density of ions in the seam between the tubular shield 89 and thewasher insulator 93, even though this seam is reasonably tight, would besufficiently great at very high welding current ranges to kindle an arcbetween the head member 86 and the gas nozzle 91 should the gas nozzlecontact the workpiece during welding. Moreover, it is significant in theoverall design of the head assembly 24 that the means for attaching thegas nozzle 91 as well as the gas nozzle itself does not extend beyondthe rearward end of the one-piece tubular shield 89 as would i be thecase, for example, if the gas nozzle were attached to the gun byconventional threaded connection rather than by the clamp 97. It isnecessary that the high density of ions present at the rearward end ofthe tubular shield 89 be free to radiate directly out into space. Suchexit is not possible if the metallic nozzle itself or some metallicmeans for holding the nozzle to the gun extends beyond the end of thetubular shield 89 since such an extension or overhang produces a cavityor seam within which the high density of ions initiate an are betweenthe nozzle and the head member or other adjacent element of the weldingcurrent circuit.

At its forward end, the tubular shield 89 extends slightly forwardly ofthe truncated cone formation comprising the forward end portion of thehead member 86. It has been found that the tubular shield 89 need notextend as far forwardly as the current contact tip 37 even though thereis extensive thermionic emission from the highly heated current contacttip 37 and the electrode 28 in this region. In fact, because of veryhigh heat radiation conditions, it is not practical to extend thetubular shield 89 into this region. Nevertheless, there is efficientsuppression of arcing to the gas nozzle in this region principally fortwo reasons: (I) as seen in FIG. 4, the spacing between the outersurface of the current contact tip 37 and the inner surface of the gasnozzle 91 is substantial; and (2) the annularly configurated shieldinggas stream in this region acts to continuously purge the space adjacentthe inner wall of the gas noule of ion concentration.

At this juncture, it will prove helpful to consider the means employedfor channeling the shielding gas through the gun to purge the chamber ofthe gas nozzle and blanket the welding operation.

As previously noted, the shielding gas from the hose 46 is directed intothe bore 44 of the main trunk 21 by the inlet tube 45 which conducts thegas to the head assembly 24. From FIG. 4, it is apparent that theshielding gas will flow from the bore 44 of the main trunk into theenlarged diameter region of the head member bore 87 which serves as apressure chamber. The shielding gas flows out of this pressure chamberthrough a ring of ports 95 into the annular cavity defined by theexposed interior surface of the tubular shield 89 and the forwardreduced diameter portion of the head member 86. There are preferably sixsuch annularly arranged ports to provide proper distribution forannularly-shaped flow. However, a greater or lesser number of ports mayalso be found practical. It is important to note two characteristics ofthe ports 95. First, the ports 95 have their exit orifices in thereduced diameter cylindrical portion of the head member outer surface sothat the possibility of plugging due to weld spatter is minimized.Second, the ports 95 are each inclined forwardly at an angle ofapproximately 30 relative to the internal surface of the tubular shield89, as illustrated in FIG. 4. Consequently, the gas flowing out of theports 95 at high velocity impinges substantially tangentially againstthe interior surface of the tubular shield 89 and flows along theinterior surface of the tubular shield 89 and the forward exposedportion of the interior surface of the gas nozzle 91, as indicated bythe flow arrows. This annular stream is substantially laminar and actsto purge the region adjacent the exposed interior surface of the gasnozzle 91 to reduce the extent of ion density in this region.

THE WELDING CURRENT CONTACT TIP The welding current contact tip 37 ofthe present invention is characterized by two salient features: (1) aninexpensive structure which provides an improved method of securing thecurrent contact tip in the head member bore, and (2) an inexpensivemethod of manufacture which provides improved wear properties in thecurrent contact tip. Consideration will be given first to the manner inwhich the current contact tip is secured in the head member bore 87.

The current contact tip 37 of the present invention is simple inconfiguration. It is not threaded and, hence, approaches the simplicityof a short length of plain, heavy wall copper tube. It is locked in thebore 87 of the head member by cam action. In brief, the structure of thecurrent contact tip 37 embodies an annularly-oriented eccentric cam orcurved wedge surface 101 (FIG. 5). The curved wedge surface comes incontact with a follower surface 102 which is stationary in relation tothe head member 86 so that when the current contact tip is turned withinthe head member bore 87, a binding force is developed between the curvedwedge surface 101 and the stationary follower surface 102 which clampsthe current contact tip within the bore 87. As best illustrated in FIG.12, the cam surface 101 forms the floor of a channel recess in thecylindrical outer surface of the current contact tip which recess isspaced forwardly from the rearward end of the current contact tip sothat an annularly oriented flange 103 is fon'ned to prevent the currentcontact tip from being pushed forwardly out of the head member 86 byunusually high amount of friction which the electrode 28, passingthrough the current contact tip bore 38, develops. The follower surface102 is at the end of a projection 104 extending radially into the headmember bore 87. As illustrated in FIGS. 4, 5, and 6, the projection 104is preferably in the form of a set screw threaded through the wall ofthe head member 86 with a flat end face, commonly called a half-dog end,to serve as the follower surface 102. Although the projection could alsobe integral with the head member, the use of a set screw for thispurpose provides a means for adjusting the clamping action employed tohold the current contact tip 37 in the head member bore 87. As shown inFIGS. 5 and 12, a recessed land 105 is provided in the outer surface ofthe current contact tip to extend as a guideway from the rearward end ofthe current contact tip to the starting end of the cam surface 101 atthe same depth as the starting end of the cam surface 101. Accordingly,when the current contact tip 37 is inserted rearwardly into the headmember bore 87, it is rotated until the land 105 registers with the setscrew projection 104 whereupon the current contact tip is moved furtherrearwardly in the head member bore 87 until the set screw 104 registerswith the cam surface 101 and is then rotated to bring the cam surfaceinto binding engagement with the set screw follower surface 102. Thesidewalls of the annular recess channel 100 prevent axial dislocation ofthe current contact tip 37 in the head member bore 87.

It should be noted from FIG. 4 that the set screw projection 104 islocated in the enlarged diameter section of the head member bore 87 sothat the point on surface of the current contact tip 37 diametricallyopposite from the point of contact of the current contact tip with theset screw projection 104 is unsupported. More specifically, the rearwardend portion of the current contact tip 37 is cantilevered in theenlarged diameter section of the bore 87 with the result that the forcedeveloped at the point of contact with the set screw projection 104causes the current contact tip to flex slightly but without exceedingthe elastic limit of the current contact tip. It is intended that evenif the current contact tip 37 is forcibly rotated 360 against the setscrew projection 104, the elastic limit of the current contact tip willnot be exceeded in flexing and that the follower surface 102 will merelybe returned to the base starting point of the cam surface 101. In thisway the current contact tip is effectively held at three points of forcecontact along its length, one force contact point being the point ofcontact with the set screw projection 104, the second being on theopposite side of the current contact tip and adjacent the rearward endof the smaller diameter section of the head member bore 87, and thethird being adjacent the forward end of the head member bore 87 on thesame side of the current contact tip as the set screw projection 104.Because the current contact tip 37 is slightly flexed against the setscrew projection 104, the clamping force exerted on the current contacttip will be retained as the head member 86, the set screw 104, and thecurrent contact tip 37 heat and cool and, hence, expand and contractduring welding.

To facilitate turning the current contact tip 37 in the head member borewith a wrench or pair of pliers, a flat spot such as shown at 106 inFIG. 12 is preferably provided on each side of the current contact tip37 at its forward end.

Referring now to FIG. 6, there is shown another preferred form of thecurrent contact tip in which a pair of cam surfaces 101a and 1011) areprovided in diametrically opposite relationship and with a correspondingpair of recessed land guideways 105a and 105b also in diametricallyopposite relationship. The clamping force for holding the currentcontact tip is developed in the same manner as described above. Theadvantage of the FIG. 6 form of current contact tip arises from the factthat the electrode 28 normally tends to wear the bore 38 of the currentcontact tip on one side at its outlet. Accordingly, with the FIG. 6 formof current contact tip, the life of the current contact tip can beextended by removing the current contact tip from the head member boreand refastening it in 180 rotated position.

Referring briefly to FIG. 7, there is shown still another form of thecurved wedge current contact connection concept of the presentinvention. In this case, a projection 98 is provided on the currentcontact tip while an annularly oriented channel 99 providing therequisite curved wedge cam surface is provided on the interior wall ofthe head member 86.

Consideration may now be given to the method of manufacture of thecurrent contact tip 37. For the purpose of explanation, the dimensionsof one size of current contact tip will be referred to in describing themethod of manufacture. It should be understood that the dimensions willdiffer in other sizes.

The completed tubular current contact tip 37 shown in FIG. 12 will beconsidered to have a length of 2 inches, an outside diameter of ninethirty-seconds inch, a wall thickness of 0.0806 inch, and an inside borediameter of 0.120 inch. A bore diameter of 0.120 inch is commonly usedfor applying 3/32-inch diameter electrode. This particular size andshape of current contact tip is formed from a 2-inch length section ofseamless commercial size electrolytic tough pitch copper tubing having a16-inch outside diameter with a 0.065-inch wall thickness. This 2-inchsection of commercial copper tube is Annintarl in FIG I?! anrlidentified bv reference numeral 111.

As will be seen, the present method of manufacture involves an increasein density of the copper which must be taken into account selecting theinitial length of the tubing section 111. In the present example,approximately 0.020 inch of the 2- inch length of the tube section 111is allowed for this increase in'density.

Referring now to FIGS. 16 and 17, punch press dies 112 and 113 are shownto aid in explaining the method of manufacture of the present invention.The particular design of the dies 112 and 113 does not form a part ofthis invention. Any die design which will accomplish the steps ofmanufacture of this invention may be used. Accordingly, in the interestof conciseness, the various obvious or conventional details of thestructures of the dies 112 and 113 will not be described.

Referring now specifically to FIG. 16, the die 112 is shown in closedposition. When the die is in open position, the section of commercialtube shown in FIG. 13 is dropped into the bore 114 which is 0.3125 inchin diameter and 3.750 inches deep. The upper portion of the bore 114 maybe 0.002 or 0.003 larger in diameter for ease of insertion of the tubesection 111. The bore 114 is closed at its lower end by the lower endmember 115. The piston 116 extends 2 inches below the upper end member117. The upper end member 117 is not affixed to the die 112 proper butrather is affixed to the piston 116 and to a second piston 122 by screws141 and 142, respectively, so as to travel with these pistons. It isimportant to note at this point that the 2-inch extension of the piston116 beyond the traveling upper end member 117 plus the 2-inch length ofthe tube section 111 of commercial tube (FIG. 13) would equal a distanceVi inch greater than the depth of the bore 114. Therefore, for the dieto be in closed position at the end of the stroke of the punch press(not shown) or other means employed for driving the piston 116, the2-inch length of the commercial tube section must be compressed to a1.750-inch length. Since the outside diameter of the tube section cannotexpand beyond the 0.3l25-inch diameter of the die bore 114, the wallthickness of the tube section is forced to increase by cold flow underthe compression force exerted by the piston 116, thereby reducing thediameter of the tube section bore. In accordance with the presentinvention, the density of the copper is preferably increased byreduction of the total displacement volume of the tube section. Toaccomplish this increase in density and to limit the reduction of theinitial 0.1825-inch diameter bore to a uniform 0.148 inch throughout thelength of the tube section by uniform upset of the copper throughout thelength of the tube section, a hard steel arbor 118 of 0.148-inchdiameter projects coaxially and downwardly from the forward end of thepiston 116. This arbor projects a distance greater than 2 inches fromthe forward face of the piston 116 so that it extends through the entirelength of the tube section before the compression and upsetting force isapplied to the top end of the tube section. A bore 143 is provided inthe lower end member 114 to accommodate the forward end of the arbor 118when the die 112 is closed as shown in FIG. 15.

The product of the compression operation performed by the die 112 isshown in FIG. 14. It consists of a second stage tube 121 of greatercopper density. Its outside diameter is 0.3125 inch; its internal or.bore diameter is 0.148 inch; its wall thickness is 0.08225 inch; itscross-sectional area is 0.0593 square inch; and its length is 1.750inches.

The die block 119 itself is preferably fitted with a second bore 114awhich is identical with the bore 114, and the die block 119 is removablefrom the die 112 proper for reversing the die block 119 end-over-end tooccupy a rotated position in the die. This reversing operation ispracticed to obtain ejection of the previously formed tube section asthe next tube is formed. More specifically, during the downstroke of thepunch press, as the section of tube in bore 114 is being compressed andupset by the piston 116, the section of tube previously compressed andupset in bore 114a is ejected by the piston 122 through a bore 144 inthe lower end member 115, as depicted in FIG. 16. Upon completion of thedownstroke of the punch press, the upstroke of the punch press isinitiated,

and the pistons 122 and 116 including the arbor 118 are completelywithdrawn from the die block bores 114 and 1140. The die block 119 isthen withdrawn from between the die side members 125 which form a stallfor the die block 119, rotated 180, and reinserted between the die sidemembers 125. In this position, the bore 114a is aligned with the piston116, and the bore 114 is aligned with piston 122 so that on the nextdownstroke of the punch press, the tube section previously compressedand upset in the bore 114 is ejected by the piston 122 as anothersection of commercial tube is being compressed and upset in the bore114a. This cycle is continuously repeated. A hairpin-shaped grippinghandle (not shown) is attached to the holes 123 to facilitate theremoval, turnover, and reinsertion of the die block 119. To insurealignment of the bores 114 and 114a with the pistons prior to eachdownstroke, a suitable retainer plate (not shown) should be provided atthe back of the die 112 and suitable latching means (not shown) providedon the front of the die 112. To prevent the die block from beingdislodged on the upstroke of the punch press, projections 124 on the dieside members 125 fit into steps 126 in the die block 119. Since the dieblock 119 is turned endover-end after each upstroke of the punch press,the steps 126 are provided at both ends of the die block 119.

The next step is forming the second stage tube 121 of FIG. 14 into thethird stage tube 131 of FIG. 15 in the die 113 shown in FIG. 17. In thisstep the following takes place: (I) the 0.3l25-inch outside diameter isreduced to 0.2812 inch; (2) the 0.1480-inch inside bore diameter isreduced to 0.120 inch; the 0.08225-inch wall thickness is reduced byapproximately 0.00 l 6 inch to a thickness of 0.0806 inch; itscross-sectional area is reduced from 0.0593 square inch to 0.0508 squareinch; and (3) the length is increased from 1.750 inches back to theoriginal length of about 2.00 inches.

The punch press die 113 is shown in closed position in FIG. 17. As seen,except for differences in the shape and dimensions of the die blockbores and the dimensions of the pistons, its structure is identical tothat of the die 112. The operation of the die 113 is as follows. Withthe die 113 open, the second stage tube 121 is dropped into the enlargeddiameter section 127 of the bore 128. The diameter of the bore section127 is 0.002 or 0.003 inch larger than the 0.3125 inch outside diameterof the second stage tube section 121 to permit easy entry of the secondstage tube into the bore section 127. The bore section 127 has a depthof 1.750 inches. At this point, the diameter of the bore 128 is reducedby a conical restriction step 133 to a diameter of 0.28l2 inch. Theincluded angle of the conical restriction 133 is 40. The bottom section134 of the bore 128 including the conical restriction step 133 is 2.00inches.

The piston 129 extends beyond the traveling top end member 132 for adistance of 1.750 inches, and its action on the downstroke of the punchpress is to force the tube in the bore section 127 to be extruded andcompressed into the reduced diameter bore section 134. To form a uniform0.120- inch inside diameter throughout the length of the extruded tube,a very high tensile strength steel wire arbor 135 (such as piano wire)of 0.120-inch outside diameter extends coaxially with and downwardlyfrom the forward end of the piston 129 for a distance greater than 2inches so that the arbor is threaded through the length of the tubebeing extruded before the extrusion begins. It should be noted that thespace between the wall of the 0.2812-inch diameter bore section and thesurface of the arbor 135 is about 0.0008 inch less than the initialthickness of the wall being extruded. The copper is thereby subjected toa second application of high compression forces to increase the lengthof the tube and increase the den' sity of the copper.

The removal of the extruded tube section from the die block 136 iscarried out in the same manner as described above in relation of the die112 of FIG. 16. The die block 136 is withdrawn, rotated 180end-over-end, and the extruded tube is pushed out of the die block bythe piston 137 on the downward stroke of the punch press simultaneouslyas another tube section is being extruded by the piston 129.

The produce of the operation of the die 113 is the third stage tubesection 131 shown in FIG. 15. Its length, outside diameter, and borediameter are that required for the finished current contact tip 37 shownin FIG. 12. The recessed curved wedge, the guideway 105, the fiat spots106, and the front end bevel 138 are provided by suitable finishingoperations.

It is important to note that respective steps performed by the dies 112and 113 may not both be necessary in forming a current contact tipaccording to the present invention. For example, if a 5/l6-inch outsidediameter current contact tip is desired instead of a 9/32-inch outsidediameter, the current contact tip may be formed from a 5/ 16-inchoutside diameter tube with a 0.065-inch wall thickness in the singlestep performed by die 112 of FIG. 16. In this case, the 0.065-inch wallwould be upset by compression force to increase it to a 0.138- inch wallto provide a 0.036-inch diameter bore. The point is that only the stepperformed by the die 112 is necessary if the ultimate current contacttip is to have approximately the same diameter as the commercial tubingfrom which it is formed since any size smaller internal bore can beprovided by the compression upset operation performed by the die 112. Ofcourse, the die bore lengths, piston lengths, arbor diameter, andrelated dimensions of the die will vary. But the compression upsetoperation itself is capable of converting a commercial size of seamlesscopper tube into a tube of any size smaller internal bore diameter. Thesecond extrusion step is performed if a reduction in outside diameter isrequired. It is also important to note that the increase in densityobtained in the copper tubing is accompanied by a refinement of thegrain structure of the copper with the result that the current contacttip so produced has a greater hardness and, hence, a greater life.Accordingly, the method herein described may be employed to greatadvantage in manufacturing current contact tips not only of the presentdesign but also of threaded and other conventional designs.

Also, it is important to note that in carrying out the present inventionthe arbors 118 and may be omitted in many cases since even without thesearbors the processes described above and illustrated in FIGS. 16 and 17will yield a current contact tip of refined grain structure andincreased hardness having a smooth, uniform bore with an internaldiameter accurate to within plus or minus 0.002 inch. When the internaldiameter must be accurate to plus or-minus 0.001 inch, the arbors 118and 135 should be used.

While several specific forms of the present invention have beenillustrated and described, it is to be understood that this is merely byway of example and in no manner to be construed as a limitation. It iscontemplated that certain modifications may be made within the scope ofthe claims without departing from the spirit of the invention.

It will be noted that in this detailed description, the expressioncurrent contact tip" has been used to refer to a particular part of thearc welding gun since this expression is commonly used in the art.However, in the claims, clarity in defining structural relationshipswill be promoted by using the expression current contact member todesignated this part.

It should also be noted that the expression ion impervious" has beenused both in the detailed description and in the claims to expresscharacteristic of the tubular shield 89 in preventing appreciable iondensity in or ion flow through the space occupied by said tubular shieldin the defined arc welding gun environment. This expression is notintended to preclude de minimus ion presence or movement in the materialof which the tubular shield is formed.

We claim:

1. In an arc welding gun for applying continuous-feed,consumable-electrode arc welding processes and which has a head memberat its arc end with a bore receiving a current contact member, and aradial adjustable element projecting radially into the head member borewherein the improvement comprises: said current contact member being atubular elec- .trically conductive current contact member having atleast one annularlyeoriented recessed channel in said current contactmember periphery and a longitudinally-oriented land in the periphery ofsaid current contact member extending from the deepest portion of saidrecessed channel to one end of said current contact member to enableregistration of said projecting element with said recessed channel whensaid current contact member is inserted into said head member bore, saidrecessed channel having for its base surface an annularlyorientedeccentric curved-wedge cam surface engaging and wedging radially againstsaid projecting element when said current contact member is compatiblypositioned and rotated within said head member bore.

2. The improvement defined in claim 1 wherein said tubular currentcontact member has a pair of diametrically-opposed flat spots in itsperiphery to facilitate gripping said current contact member to rotatesaid current contact member within said head member bore.

3. In an arc welding gun for applying continuous-feed,consumable-electrode arc welding processes and which has a head memberat its arc end with a bore receiving a current contact member, and anelement projecting radially into the head member bore, wherein theimprovement comprises: said current contact member being a tubularelectrically conductive current contact member having a pair ofannularlyoriented recessed channels disposed in diametrically oppositerelationship in said current contact member periphery and a pair oflongitudinally-oriented lands disposed in diametrically oppositerelationship in the periphery of said current contact member, each ofsaid lands extending from the deepest portion of an associated one ofsaid pair of recessed channels to one end of said current contact memberto permit registration of said projecting element selectively with saidassociated recessed channel when said current contact member is insertedinto said head member bore, each of said recessed channels having forits base surface an annularly-oriented eccentric curved-wedge camsurface engaging and wedging radially against said projecting elementwhen said current contact member is compatibly positioned and rotatedwithin said head member bore thereby enabling said current contactmember to be selectively wedged within said head member bore in eitherof two rotated orientations.

4. In an arc welding gun for applying continuous-feed,consumable-electrode arc welding processes and which has a head memberat its arc end with a bore receiving a current contact member, and anadjustable set screw projecting radially into said head member bore, theimprovement comprising: said current contact member being a tubularelectrically conductive current contact member having at least oneannularly-oriented eccentric curved-wedge cam surface in its peripheryengaging and wedging radially against said set screw when said currentcontact member is compatibly positioned and rotated within said headmember bore, and a step in said head member bo're forwardly of said setscrew enlarging the diameter of said head member bore for the portion ofits length in which said cam surface coacts with said set screw leavingthe periphery of said current contact member diametrically opposite thepoint of coactionof said projecting element unsupported to permit slightflexing of said current contact member when cam surface is wedgedagainst said set screw.

Patent No. 3 576, 42} Dated April 27, 1971 Invento -(s) A. and A.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Title page, "Assignee Bernard Welding Equipment Company, Beecher, I11.should read --Assignee Dover Corporation, New York, N. Y.

In the Abstract, line 9, "top" should read --tip-- Column 6, lines 6 1,65, "and inch" should read --inch and 5/8 inch.--

Column 11, line 1, "in" should read --is-- Column 16, line 3, "produce"should read --product-- line 60, "designated" should read --designate--In the claims: Column 17, line 2, "annularlyeoriented" should read--annu1arly oriented-- Signed and sealed this 9th day of November 1971.

(SEAL) Esteem:

WARD M.FLETCHER,JR. ROBERT GO'I'TSCHALK Attosting Officer ActingCommissioner of Patents

1. In an arc welding gun for applying continuous-feed,consumable-electrode arc welding processes and which has a head memberat its arc end with a bore receiving a current contact member, and aradial adjustable element projecting radially into the head member borewherein the improvement comprises: said current contact member being atubular electrically conductive current contact member having at leastone annularly-oriented recessed channel in said current contact memberperiphery and a longitudinally-oriented land in the periphery of saidcurrent contact member extending from the deepest portion of saidrecessed channel to one end of said current contact member to enableregistration of said projecting element with said recessed channel whensaid current contact member is inserted into said head member bore, saidrecessed channel having for its base surface an annularly-orientedeccentric curved-wedge cam surface engaging and wedging radially againstsaid projecting element when said current contact member is compatiblypositioned and rotated within said head member bore.
 2. The improvementdefined in claim 1 wherein said tubular current contact member has apair of diametrically-opposed flat spots in its periphery to facilitategripping said current contact member to rotate said current contactmember within said head member bore.
 3. In an arc welding gun forapplying continuous-feed, consumable-electrode arc welding processes andwhich has a head member at its arc eNd with a bore receiving a currentcontact member, and an element projecting radially into the head memberbore, wherein the improvement comprises: said current contact memberbeing a tubular electrically conductive current contact member having apair of annularly-oriented recessed channels disposed in diametricallyopposite relationship in said current contact member periphery and apair of longitudinally-oriented lands disposed in diametrically oppositerelationship in the periphery of said current contact member, each ofsaid lands extending from the deepest portion of an associated one ofsaid pair of recessed channels to one end of said current contact memberto permit registration of said projecting element selectively with saidassociated recessed channel when said current contact member is insertedinto said head member bore, each of said recessed channels having forits base surface an annularly-oriented eccentric curved-wedge camsurface engaging and wedging radially against said projecting elementwhen said current contact member is compatibly positioned and rotatedwithin said head member bore thereby enabling said current contactmember to be selectively wedged within said head member bore in eitherof two 180* rotated orientations.
 4. In an arc welding gun for applyingcontinuous-feed, consumable-electrode arc welding processes and whichhas a head member at its arc end with a bore receiving a current contactmember, and an adjustable set screw projecting radially into said headmember bore, the improvement comprising: said current contact memberbeing a tubular electrically conductive current contact member having atleast one annularly-oriented eccentric curved-wedge cam surface in itsperiphery engaging and wedging radially against said set screw when saidcurrent contact member is compatibly positioned and rotated within saidhead member bore, and a step in said head member bore forwardly of saidset screw enlarging the diameter of said head member bore for theportion of its length in which said cam surface coacts with said setscrew leaving the periphery of said current contact member diametricallyopposite the point of coaction of said projecting element unsupported topermit slight flexing of said current contact member when cam surface iswedged against said set screw.